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Limbus Sign
The limbus sign is a ring of dystrophic calcification evident as a "milky precipitate" (i.e. abnormal white color) at the corneal limbus. The corneal limbus is the part of the eye where the cornea (front/center) meets the sclera (white part of the eye). Thought to be caused by increased calcium concentration in the blood, this sign however persists after calcium phosphate concentration returns to normal. Compare the limbus sign (calcification) with arcus senilis Arcus senilis (AS), also known as gerontoxon, arcus lipoides, arcus corneae, corneal arcus, arcus adiposus, or arcus cornealis, are rings in the peripheral cornea. It‘s usually caused by cholesterol deposits, so it may be a sign of high choleste ... (lipid).Edwards, Mark E. (2008)Geriatric physical diagnosis: a guide to observation and assessment.McFarland & Company. p. 96. Retrieved January 7, 2012. References {{med-sign-stub Eye Medical signs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dystrophic Calcification
Dystrophic calcification (DC) is the calcification occurring in degenerated or necrotic tissue, as in hyalinized scars, degenerated foci in leiomyomas, and caseous nodules. This occurs as a reaction to tissue damage, including as a consequence of medical device implantation. Dystrophic calcification can occur even if the amount of calcium in the blood is not elevated (a systemic mineral imbalance would elevate calcium levels in the blood and all tissues) and cause metastatic calcification. Basophilic calcium salt deposits aggregate, first in the mitochondria, then progressively throughout the cell. These calcifications are an indication of previous microscopic cell injury, occurring in areas of cell necrosis when activated phosphatases bind calcium ions to phospholipids in the membrane. Calcification in dead tissue #Caseous necrosis in T.B. is most common site of dystrophic calcification. #Liquefactive necrosis in chronic abscesses may get calcified. #Fat necrosis following acu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precipitate
In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading to precipitation, the chemical reagent causing the solid to form is called the ''precipitant''. The clear liquid remaining above the precipitated or the centrifuged solid phase is also called the 'supernate' or 'supernatant'. The notion of precipitation can also be extended to other domains of chemistry (organic chemistry and biochemistry) and even be applied to the solid phases (''e.g.'', metallurgy and alloys) when solid impurities segregate from a solid phase. Supersaturation The precipitation of a compound may occur when its concentration exceeds its solubility. This can be due to temperature changes, solvent evaporation, or by mixing solvents. Precipitation occurs more rapidly from a strongly supersaturated solution. The formati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corneal Limbus
The corneal limbus (''Latin'': corneal border) is the border between the cornea and the sclera (the white of the eye). It contains stem cells in its palisades of Vogt. It may be affected by cancer or by aniridia (a developmental problem), among other issues. Structure The corneal limbus is the border between the cornea and the sclera. It is highly vascularised. Its stratified squamous epithelium is continuous with the epithelium covering the cornea. The corneal limbus contains radially-oriented fibrovascular ridges known as the palisades of Vogt that contain stem cells. The palisades of Vogt are more common in the superior and inferior quadrants around the eye. Clinical significance Cancer The corneal limbus is a common site for the occurrence of corneal epithelial neoplasm. Aniridia Aniridia, a developmental anomaly of the iris, disrupts the normal barrier of the cornea to the conjunctival epithelial cells at the limbus. Glaucoma The corneal limbus may be c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43 dioptres. The cornea can be reshaped by surgical procedures such as LASIK. While the cornea contributes most of the eye's focusing power, its focus is fixed. Accommodation (the refocusing of light to better view near objects) is accomplished by changing the geometry of the lens. Medical terms related to the cornea often start with the prefix "'' kerat-''" from the Greek word κέρας, ''horn''. Structure The cornea has unmyelinated nerve endings sensitive to touch, temperature and chemicals; a touch of the cornea causes an involuntary reflex to close the eyelid. Because transparency is of prime importance, the healthy cornea does not have or need blood vessels with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sclera
The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some crucial elastic fiber. In humans, and some other vertebrates, the whole sclera is white, contrasting with the coloured iris, but in most mammals, the visible part of the sclera matches the colour of the iris, so the white part does not normally show while other vertebrates have distinct colors for both of them. In the development of the embryo, the sclera is derived from the neural crest. In children, it is thinner and shows some of the underlying pigment, appearing slightly blue. In the elderly, fatty deposits on the sclera can make it appear slightly yellow. People with dark skin can have naturally darkened sclerae, the result of melanin pigmentation. The human eye is relatively rare for having a pale sclera (relative to the iris). This makes it easier for one individual to ide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcium Phosphate
The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. Calcium phosphates are white solids of nutritious value and are found in many living organisms, e.g., bone mineral and tooth enamel. In milk, it exists in a colloidal form in micelles bound to casein protein with magnesium, zinc, and citrate–collectively referred to as colloidal calcium phosphate (CCP). Various calcium phosphate minerals are used in the production of phosphoric acid and fertilizers. Overuse of certain forms of calcium phosphate can lead to nutrient-containing surface runoff and subsequent adverse effects upon receiving waters such as algal blooms and eutrophication (over-enrichment with nutrients and minerals). Orthophosphates, di- and monohydrogen phosphates These materials contain Ca2+ combined with , , or : * Monocalcium phosphate, E341 (CAS# 775 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arcus Senilis
Arcus senilis (AS), also known as gerontoxon, arcus lipoides, arcus corneae, corneal arcus, arcus adiposus, or arcus cornealis, are rings in the peripheral cornea. It‘s usually caused by cholesterol deposits, so it may be a sign of high cholesterol. It is the most common peripheral corneal opacity, and is usually found in the elderly where it is considered a benign condition. When AS is found in patients less than 50 years old it is termed arcus juvenilis. The finding of arcus juvenilis in combination with hyperlipidemia in younger men represents an increased risk for cardiovascular disease. Pathophysiology AS is caused by leakage of lipoproteins from limbal capillaries into the corneal stroma. Deposits have been found to consist mostly of low-density lipoprotein (LDL). Deposition of lipids into the cornea begins at the superior and inferior aspects, and progresses to encircle the entire peripheral cornea. The interior border of AS has a diffuse appearance, while the exterior b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
